1. Field of the Invention
The present invention relates to a printing apparatus such as an inkjet printing apparatus and a method for adjusting printing position thereof.
2. Description of the Related Art
Japanese Patent No. 3554184 discloses a printing position adjustment method in an inkjet printing apparatus. More specifically, a “reference pattern” is printed by a reference nozzle array, after which a plurality of “shifted patterns”, which are printed from a different nozzle array whose printing position is shifted a little at a time from the reference pattern, are printed over the reference pattern. Then based on the amount that the printing position of the shifted pattern is shifted and the position of the inflection point of the optical reflectivity, the amount of shift in the landing position is calculated and the discharge timing that the printing head discharges ink is corrected.
In the method disclosed in Japanese Patent No. 3554184, in order to achieve a highly-accurate adjustment of the landing position, the calculation error must be reduced by matching the approximation curve and the optical characteristics well. Therefore, it is preferred to calculate an approximate expression from an optical reflectivity that is near the inflection point and within a smaller shift range. However, by using a change of the amount of shift within a smaller range, the change of the optical reflectivity is also smaller. As a result, the effect of a disturbance such as noise cannot be ignored and sufficient accuracy cannot be obtained.